A transparent electrode has been widely used in various industrial fields such as a thin film transistor (TFT) element, a solar cell, a touch screen, and the like.
According to the related art, a material for the transparent electrode, indium tin oxide (ITO) is mainly used, but there are problems such as depletion of indium and process complexity. In addition, since deposition of ITO is mostly performed by a thin film deposition process, there are problems in that a process cost is expensive, and cracks occur due to formation of a dense thin film having a crystalline structure. Therefore, ITO has a disadvantage in that ITO is not suitable for a transparent electrode using a flexible substrate using polymers, which is recently spotlighted. Recently, as a material for replacing an ITO transparent material, silver nanowires have been spotlighted.
Meanwhile, a production method for a flexible transparent electrode is largely divided into a method using metal ink to utilize nano mesh and a method using metal nanowires represented by silver nanowires. Among them, a core technology in the case of producing a transparent electrode by seating metal nanowires on a flexible substrate is an adhesion method for the metal nanowires.
As an example, according to the related art, in order to adhere the metal nanowires, a method of applying high heat (200 to 350° C.) in an inert gas, a laser irradiation method, or a chemical method was used. However, these methods have disadvantages in that a long time is consumed, a melting point is low, and it is impossible to use these methods in a polymer substrate which may cause chemical reactions. Further, a technology for producing a transparent electrode by adhering silver nanowires using light sintering was disclosed in Korean Patent Laid-Open Publication No. 2012-0092294, but sheet resistance uniformity is deteriorated, such that there is a limitation in commercializing this method.
Further, at the time of coating metal nanowires on a substrate to form a film, it is important to uniformly coat the metal nanowires. In general, it is known that since the metal nanowires including silver nanowires have strong cohesive force between themselves, in the case of dispersing the metal nanowires in a solvent such as water, Or the like, it is difficult to obtain uniform dispersibility, and particularly, in the case of coating the metal nanowires on a substrate to dry the coated metal nanowires, as a solvent volatilizes first, the metal nanowires are aggregated with each other, such that, it is difficult to uniformly form the metal nanowires forming a surface coating layer on the substrate, and as a result, it is significantly difficult to provide a transparent electrode film having uniform sheet resistance on an entire surface thereof.
Therefore, in order to provide a transparent electrode capable of being applied as a flexible transparent electrode using a polymer material and having uniform sheet resistance on an entire surface thereof, there is a need to develop a transparent electrode film capable of being adhered within a significantly short time at room temperature under atmospheric conditions and having improved sheet resistance uniformity without affecting other components through chemical reactions.